Re: [PATCH v4 1/3] libceph: fail the sparse-read if there still has data in socket

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On 1/19/24 19:03, Jeff Layton wrote:
On Fri, 2024-01-19 at 12:07 +0800, Xiubo Li wrote:
On 1/18/24 22:03, Jeff Layton wrote:
On Thu, 2024-01-18 at 18:50 +0800, xiubli@xxxxxxxxxx wrote:
From: Xiubo Li <xiubli@xxxxxxxxxx>

Once this happens that means there have bugs.

Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
   net/ceph/osd_client.c | 9 +++++++++
   1 file changed, 9 insertions(+)

diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 9be80d01c1dc..f8029b30a3fb 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -5912,6 +5912,13 @@ static int osd_sparse_read(struct ceph_connection *con,
   		if (sr->sr_index >= count) {
+			if (sr->sr_datalen) {
+				pr_warn_ratelimited("sr_datalen %u sr_index %d count %u\n",
+						    sr->sr_datalen, sr->sr_index,
+						    count);
+				return -EREMOTEIO;
+			}
Ok, so the server has (presumably) sent us a longer value for the
sr_datalen than was in the extent map?

Why should the sparse read engine care about that? It was (presumably)
able to do its job of handling the read. Why not just advance past the
extra junk and try to do another sparse read? Do we really need to fail
the op for this?
Hi Jeff,

I saw the problem just when I first debugging the sparse-read bug, and
the length will be very large, more detail and the logs please see the

       11741055 <4>[180940.606488] libceph: sr_datalen 251723776 sr_index
0 count 0

In this case the request could cause the same request being retrying
infinitely. While just in other case the when the ceph send a incorrect
data length, how should we do ? Should we retry it ? How could we skip
it if the length is so large ?

If the sparse_read datalen is so long that it goes beyond the length of
the entire frame, then it's clearly malformed and we have to reject it.

I do wonder though whether this is the right place to do that. It seems
like the client ought to do that sort of vetting of lengths before it
starts dealing with the read data.

IOW, maybe there should be a simple check in the
CEPH_SPARSE_READ_DATA_LEN case that validates that the sr_datalen fits
inside the "data_len" of the entire frame?

Well it should be in CEPH_SPARSE_READ_DATA_PRE instead.

I can improve this.


- Xiubo

   			sr->sr_state = CEPH_SPARSE_READ_HDR;
   			goto next_op;
@@ -5919,6 +5926,8 @@ static int osd_sparse_read(struct ceph_connection *con,
   		eoff = sr->sr_extent[sr->sr_index].off;
   		elen = sr->sr_extent[sr->sr_index].len;
+ sr->sr_datalen -= elen;
   		dout("[%d] ext %d off 0x%llx len 0x%llx\n",
   		     o->o_osd, sr->sr_index, eoff, elen);

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